Capacity asks how much work or how many users the product can carry before a stated property fails. A measure relates the maximum acceptable load to the load the requirements state. Capacity needs a failure definition. Without one, the maximum is where the tester stopped, not where the product stopped. The property that fails might be response time, error rate, memory, or a hard stop, and each gives a different capacity figure. The data volume matters as much as the user count, and the environment matters as much as both. A capacity measure should be reported as a curve with the failure boundary marked, not as a single number.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.